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No-Vig Calculator

Enter a bookmaker's odds to strip out the vig. See the overround, the fair (no-vig) probability and odds for each outcome, and how the margin compares with Polymarket's fee.

Market
Overround
104.71%
Bookmaker margin
4.71%
OutcomeImpliedFair (no-vig)Fair decimalFair AmericanPolymarket price
Outcome 152.36%50.00%2.00+100$0.50
Outcome 252.36%50.00%2.00+100$0.50

Same market on Polymarket

Bookmaker margin
4.71%
Polymarket cost at fair prices
2.50%

Polymarket is 2.21 percentage points cheaper on this market.

Fair probabilities remove the margin proportionally: fair = implied ÷ sum of implied. Polymarket cost = feeRate × Σ p × (1 − p) per $1 of payout, priced at the fair probabilities.

How the No-Vig Calculator Works

A bookmaker’s odds always add up to more than 100%. Take a standard NFL line of -110 on both sides:

  • -110 is decimal odds of 1.91, an implied probability of 52.4%
  • Both sides together: 52.4% + 52.4% = 104.8%
  • The extra 4.8% is the overround: the bookmaker’s margin built into the prices

To find the fair odds, the calculator scales each implied probability down so the total is exactly 100%. Each side becomes 50.0%, fair decimal odds of 2.00, or +100 in American odds.

This is the proportional method, the standard way to remove vig. It spreads the margin across outcomes in proportion to their implied probability.

Why Fair Odds Matter

Fair odds tell you what a bet is actually worth. They’re useful for three things:

  • Spotting value. If another bookmaker offers better than the fair odds, the bet has positive expected value. Check it with the EV calculator.
  • Comparing bookmakers. A lower overround means you’re paying less for the same bet.
  • Checking cash-out offers. Fair value is the starting point for knowing whether a cash-out offer is reasonable.

3-Way Markets

Football match result markets have three outcomes: home win, draw, away win. Switch to 3-way and enter all three prices. Margins on 3-way markets are usually higher than on 2-way lines because there are more outcomes for the bookmaker to price.

Vig vs Polymarket’s Fee

Polymarket doesn’t build a margin into its prices. Its prices come from an order book where traders buy and sell to each other, and it charges a separate, published taker fee:

fee = shares × feeRate × price × (1 − price)

The calculator prices each outcome at its fair probability and shows what buying the whole market on Polymarket would cost: the equivalent of the bookmaker’s overround. On most sports markets (fee rate 0.05) that is about 2.5% for a 50/50 market. It falls as prices move away from 50¢, and it’s about 1.5% on NFL and college football games (0.03). Orders that rest on the book as limit orders pay no fee at all.

You’ll also cross the bid-ask spread, which is small on liquid markets. Polymarket fees covers every category, and Polymarket sports betting explains how betting on an exchange works.

Frequently Asked Questions

What is a no-vig calculator?
A no-vig calculator removes the bookmaker's margin from a set of odds. It converts each price to an implied probability, adds them up to find the overround, then scales each probability down so they sum to 100%. The result is the fair probability and fair odds for each outcome.
What is vig in betting?
Vig (also called juice, margin or overround) is the commission a bookmaker builds into its odds. Because of it, the implied probabilities of all outcomes add up to more than 100%. The excess is the bookmaker's margin.
How do you calculate the vig?
Convert each outcome's odds to an implied probability (1 ÷ decimal odds), add them together, and subtract 100%. Two outcomes at -110 (1.91) each imply 52.4%, for a total of 104.8%, so the overround is 4.8% above a fair book.
How do you calculate no-vig odds?
Divide each outcome's implied probability by the total of all implied probabilities. That gives fair probabilities that sum to 100%. Fair decimal odds are 1 divided by the fair probability.
What is a typical bookmaker margin?
Most sportsbook markets carry a margin of about 4% to 10%. Main lines on major sports are at the low end; player props, futures and niche markets are often far higher.
How does Polymarket's fee compare with the vig?
Polymarket's prices contain no margin. It charges takers a separate fee of shares × feeRate × p × (1 − p). On most sports (0.05 rate) that is about 2.5% across a 50/50 market and less at other prices; NFL and college football games (0.03) are about 1.5%. Limit orders that rest on the book pay nothing.